It's just the most insignificant example of how being even slightly outside the local cultural norms can grate on your psyche. If I can get irritated at how people around here are football obsessed, anything more significant must have a greater impact.
So if people around here are generally hostile towards homosexuality, a gay person must feel worse than I do when people start talking about specific players on specific teams and upcoming scheduled games and the keystone play of some past game and just shut up, shut up, will you please shut the hell up about football for once?!
It makes me wonder how people even further from the norm than myself can even find the strength to get up out of bed in the morning, or, once risen, get through the entire day without destroying some ignorant blatherer with a beam of pure rage exploding from their foreheads.
It's not just about being around people who are different, but having enough different people around you that you can't just assume everyone else is like you. If you don't know that someone is Muslim, and make a derogatory comment about Muslims in front of them, that person might not feel secure enough socially to confront you about it. So they keep their religion secret from you, and you might continue crapping on something important to them, without anyone ever telling you that you shouldn't do that.
If, on the other hand, you live in a city where anybody could be anything, you are more likely to encounter situations where you are the minority in some way, and therefore will probably be more sensitive to how it feels when a local majority tramples over your opinions.
You just have to realize that other people might not share your opinions, interests, and values, and if yours are part of the local majority, other people might just be humoring you to fit in better, or irritated at the constant reminders that they are not part of the dominant tribe.